Add a stack chain class to the stack trace package.

pkg/stack_trace/test/trace_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library trace_test;
 
 import 'package:path/path.dart' as path;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 153 matching lines @@
       var trace = new Trace.parse(
           'http://dartlang.org/foo/bar.dart 10:11  Foo.<fn>.bar\n'
           'http://dartlang.org/foo/baz.dart        Foo.<fn>.bar');
 
       expect(trace.frames[0].uri,
           equals(Uri.parse("http://dartlang.org/foo/bar.dart")));
       expect(trace.frames[1].uri,
           equals(Uri.parse("http://dartlang.org/foo/baz.dart")));
     });
 
+    test('parses a package:stack_trace stack chain correctly', () {
+      var trace = new Trace.parse(
+          'http://dartlang.org/foo/bar.dart 10:11  Foo.<fn>.bar\n'
+          'http://dartlang.org/foo/baz.dart        Foo.<fn>.bar\n'
+          '===== asynchronous gap ===========================\n'
+          'http://dartlang.org/foo/bang.dart 10:11  Foo.<fn>.bar\n'
+          'http://dartlang.org/foo/quux.dart        Foo.<fn>.bar');
+
+      expect(trace.frames[0].uri,
+          equals(Uri.parse("http://dartlang.org/foo/bar.dart")));
+      expect(trace.frames[1].uri,
+          equals(Uri.parse("http://dartlang.org/foo/baz.dart")));
+      expect(trace.frames[2].uri,
+          equals(Uri.parse("http://dartlang.org/foo/bang.dart")));
+      expect(trace.frames[3].uri,
+          equals(Uri.parse("http://dartlang.org/foo/quux.dart")));
+    });
+
     test('parses a real package:stack_trace stack trace correctly', () {
       var traceString = new Trace.current().toString();
       expect(new Trace.parse(traceString).toString(), equals(traceString));
     });
 
     test('parses an empty string correctly', () {
       var trace = new Trace.parse('');
       expect(trace.frames, isEmpty);
       expect(trace.toString(), equals(''));
     });
@@ skipping 57 matching lines @@
 
     var folded = trace.foldFrames((frame) => frame.member.startsWith('foo'));
     expect(folded.toString(), equals('''
 foo.dart 42:21                     notFoo
 foo.dart 1:100                     fooBottom
 bar.dart 10:20                     alsoNotFoo
 dart:async-patch/future.dart 9:11  fooBottom
 '''));
   });
 }